ALBERT

Description: Introduction Patients with relapsed or refractory (R/R) MYC-altered DLBCL have poor outcomes, and other than for a subset of patients who may benefit from chimeric antigen receptor T cell therapy, no treatment has shown a significant durable benefit or impact on survival outcomes. Fimepinostat is a first-in-class, well-tolerated, oral small molecule inhibitor of HDAC and PI3K enzymes. There is particular interest in evaluating fimepinostat in patients with MYC-dependent tumors as nonclinical studies demonstrated that fimepinostat inhibits transcription of MYC and a subset of MYC-associated genes. Additionally, MYC protein levels were downregulated by fimepinostat in part through inhibition of PI3K-mediated ubiquitination. Pharmacodynamic inhibition of HDAC and PI3K has also been demonstrated in human studies. Here we report the outcome of R/R DBLCL patients treated with fimepinostat in a Phase 1 and Phase 2 study, with an emphasis on outcomes for patients with MYC-altered disease. Patients and Methods A total of 105 R/R DLBCL patients were enrolled on the Phase 1 study CUDC-907-101 (n = 37) and the Phase 2 study CUDC-907-201 (n = 68). In CUDC-907-101, 14 patients were found to have MYC-altered disease, defined as presence of MYC rearrangement by either central or local testing by fluorescent in situ hybridization or MYC protein expression ≥40%) by immunohistochemistry (IHC). In CUDC-907-201, 46 patients had confirmed MYC-altered disease by central IHC testing. Across both studies, patients without available tissue or prior test results were deemed as MYC-status unknown (n = 23). Results A total of 19 responses (9 CR, 10 partial responses [PR]) were reported across both studies. The objective response rate (ORR) in MYC altered patients was 23.3% (14/60). Responses showed encouraging durability with a median duration of response of 13.6 months (range: 2.8 to Not Calculable [NC]). Five MYC-altered responses were ongoing as of the data-cut. Two MYC-altered patients achieving CR discontinued treatment early to pursue stem cell transplantation. Responses associated with fimepinostat often require multiple cycles of treatment to manifest (median time to first response = 2.5 months for MYC-altered patients), and of patients who were treated for ≥2 months, a large proportion (17/33; 52%) achieved a response. Patients with low disease burden at screening (tumor lesions diameters ≤ 5 cm and lactate dehydrogenase [LDH] 〈 1.5 x upper limit of normal [ULN]) generally continued treatment longer and were most likely to derive clinical benefit (Table 2). Conclusions The biologic rationale, tolerable safety profile, and evidence of durable anti-tumor activity in MYC-altered R/R DLBCL support the continued development of fimepinostat in this poor-prognosis patient population. Patients with low disease burden features may be more likely to have sufficient duration of drug exposure to allow clinical benefit. Future enrollment will focus on patients with screening characteristics most likely to derive the greatest benefit from fimepinostat treatment. Disclosures Landsburg: Takeda: Consultancy; Curis: Consultancy, Research Funding. Ramchandren:Seattle Genetics: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy; Merck: Research Funding; Pharmacyclics LLC an AbbVie Company: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Lugtenburg:Millennium/Takeda: Consultancy, Research Funding; Servier: Consultancy, Research Funding; Roche: Consultancy; BMS: Consultancy; Sandoz: Consultancy; Genmab: Consultancy. Younes:Takeda: Honoraria; Abbvie: Honoraria; BMS: Honoraria, Research Funding; Novartis: Research Funding; Curis: Research Funding; Incyte: Honoraria; Seattle Genetics: Honoraria; Janssen: Honoraria, Research Funding; Bayer: Honoraria; Sanofi: Honoraria; Astra Zeneca: Research Funding; Celgene: Honoraria; J&J: Research Funding; Pharmacyclics: Research Funding; Roche: Honoraria, Research Funding; Merck: Honoraria; Genentech: Research Funding. Tuck:Curis, Inc: Employment, Equity Ownership. Barta:Janssen: Membership on an entity's Board of Directors or advisory committees; Merck, Takeda, Celgene, Seattle Genetics, Bayer: Research Funding.

Description: CUDC-907 is a first-in-class, oral, dual inhibitor of Class I and II HDAC, as well as Class I PI3K enzymes. Specifically, CUDC-907 is designed to inhibit HDACs 1, 2, 3, 6 and 10 and PI3K-alpha, delta and beta isoform. Preclinical studies demonstrate that CUDC-907 has potent effects on acetylated histone-regulated genes and PI3K signaling. CUDC-907 showed potent antitumor activity in multiple preclinical tumor models as well as in patients with relapsed or refractory diffuse large B-cell lymphoma (RR DLBCL), with objective responses reported in multiple patients, including complete responses. It is currently being investigated in a Phase 2 study in patients with RR DLBCL, including those with MYC-alterations. Preclinical studies of CUDC-907 in combination with chemotherapeutic and targeted agents are in progress. Venetoclax, a BH3 mimetic and selective BCL2 inhibitor, was recently approved for the treatment of patients with chronic lymphocytic leukemia (CLL) whose tumors had a 17p deletion. Results from a Phase 1 study of venetoclax monotherapy in patients with relapsed or refractory non-Hodgkin lymphoma showed that patients with DLBCL exhibited short-lived responses to venetoclax. Thus, combination approaches may be required to achieve durable responses to venetoclax in DLBCL. In our preclinical studies, we examined the combination of venetoclax and CUDC-907 in DLBCL cell lines. Interestingly, the combination exhibited the most synergy, as measured by fold-improvement over predicted additive effect, in cell lines insensitive to venetoclax. For example, OCI-Ly3 cells were insensitive to single agent venetoclax with an IC50 〉10uM; however, in combination with a fixed dose (12nM) of CUDC-907, venetoclax resulted in 〉10000-fold improvement in potency with a combination IC50 of 0.001uM. Synergy was also observed in tumor growth inhibition studies in xenograft models. Western blot analysis showed that single-agent CUDC-907 simultaneously increased pro-apoptotic BIM protein and decreased anti-apoptotic BCL2 protein levels. Interestingly, the low nano-molar concentrations of CUDC-907 that were shown to regulate the BCL-2 family member proteins could also potentiate pro-apoptotic effects of venetoclax when used together in combination in WSU-DLCL2 cell line which carries MYC and BCL2 translocations. Thus, the effect of CUDC-907 on BCL2 family members appears to be the basis for the observed synergy with venetoclax, which functions to displace BIM from BCL2. These results provide a mechanistic rationale for the use of CUDC-907 in combination with venetoclax for the treatment of patients with DLBCL. Disclosures Sun: Curis: Employment, Equity Ownership. Atoyan:Curis: Employment, Equity Ownership. Borek:Curis: Employment, Equity Ownership. Dellarocca:Curis: Employment, Equity Ownership. Rhyasen:Curis: Employment, Equity Ownership. Fattaey:Curis: Employment, Equity Ownership. Tuck:Curis, Inc.: Employment, Equity Ownership.

Description: Background: IRAK4 kinase activity is required for toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) signaling in a variety of myeloid and lymphoid cell types. Recruitment of IRAK4 to these receptors and its subsequent activation is facilitated by the MYD88 adaptor protein. The MYD88-L265P activating mutation is prevalent in DLBCL (~30% in ABC subtype) and WM (〉90%). MYD88- L265P leads to constitutive activation of NF-κB signaling that is associated with worse prognosis. In MCL, dysregulation of B-cell receptor (BCR) and TLR pathway components correlate with constitutive NF-κB signaling. CA-4948 is a small molecule inhibitor of IRAK4 kinase that modulates the TLR and IL-1R signaling cascades. CA-4948 is being developed as a novel agent for the treatment of hematologic cancers with dysregulated IRAK4 signaling and is currently in a Ph1 trial for R/R NHL (clinicaltrials.gov NCT03328078). In preclinical studies, CA-4948 demonstrates pharmacodynamic and antitumor activity in in vitro and in vivo models with MYD88 alterations, and was previously shown to have a synergistic anti-tumor activity when combined with venetoclax in vivo. To further guide CA-4948's clinical development in NHL, we report here nonclinical studies exploring a twice-daily dosing schedule in DLBCL xenograft models. We also investigated the use of an ex-vivo whole-blood TLR-stimulation assay as a surrogate PD response biomarker. Additionally, we tested the efficacy of CA-4948 alone or in combination with the BTK inhibitor ibrutinib in DLBCL and MCL tumor models. Furthermore, preliminary PK and PD data from the first-in-human Ph1 trial are presented. Methods: Mice bearing DLBCL PDX tumors were orally administered CA-4948 twice-daily (BID) with 37.5 or 75 mg/kg doses and once-daily (QD) with 75 or 150 mg/kg doses. The ex-vivo whole blood assay involved TLR-stimulation of blood isolated at various time-points after CA-4948 administration. For the drug combination studies, mice bearing subcutaneous tumors of a MYD88-L265P DLBCL cell line or six MCL cell lines were treated. Results: (1) CA-4948 exhibited dose-dependent tumor growth inhibition in two DLBCL PDX xenograft tumor models with BID dosing showing equal or enhanced efficacy as compared to the equivalent total daily QD dose. The BID schedule was well tolerated with only a slight body weight loss as compared to the equivalent total QD dose schedule. (2) Overall, in mouse, the ex-vivo blood assay showed a time and exposure dependent relationship with the level of cytokine production after TLR-stimulation. A similar CA-4948 dose-dependent inhibition of TLR-stimulated cytokine production was observed in healthy human whole blood samples in which CA-4948 was spiked into the blood sample. Based on these findings, CA-4948 exposure levels capable of inhibiting TLR-stimulation are anticipated to be readily achievable in clinical studies. This was also supported by preliminary clinical PD data showing post treatment, on-target, reduced release of NF-κB-associated cytokines in 2 of 4 patients treated so far. (3) In xenograft efficacy studies using MCL models, single agent CA-4948 and ibrutinib exhibited anti-tumor activity and showed an additive effect when combined in the majority of the models known to have BCR-driven constitutive canonical NF-kB signaling (REC-1, MINO, and JeKo-1). Interestingly, neither CA-4948, ibrutinib, nor the combination had anti-tumor activity in Z-138 and GRANTA-591 xenograft models, consistent with these cell lines having activated NF-κB through the alternative NIK signaling pathway. (4) The human QD PK data (n=4) demonstrated that CA-4948: was rapidly absorbed, Tmax 1-3 hr, and t1/2 of 3.6 -6.8 hr. The bioavailability and exposure, as assessed by Cmax and AUC, is within the expected range compared to non-clinical PK and did not show any evidence of accumulation after QD dosing for 15 consecutive days. Conclusion: These results provide a rationale for CA-4948 BID dosing and incorporating the use of an ex-vivo whole-blood TLR-stimulation assay as a surrogate PD response biomarker, the former of which will be evaluated in the current Ph1 dose escalation soon and the latter of which is currently being implemented in the Ph1 trial for patients with advanced NHL. The murine xenograft results further support exploration of CA-4948 as monotherapy and in combination with canonical and alternative NF-κB pathway-targeted agents in DLBCL and MCL. Disclosures Booher: Curis, Inc: Employment, Equity Ownership. Patel:Juno Therapeutics: Consultancy; Pharmacyclics/Janssen: Speakers Bureau; Genentech: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Celgene: Consultancy; Sunesis Pharmaceuticals: Consultancy. Lunning:Celgene: Consultancy; AbbVie: Consultancy; Astra-Zeneca: Consultancy; Bayer: Consultancy; Genentech: Consultancy; Genzyme: Consultancy; Genentech: Consultancy; Gilead: Consultancy; Janssen: Consultancy; Juno: Consultancy; Kite: Consultancy; Portola: Consultancy; Seattle Genetics: Consultancy; Spectrum: Consultancy; TG Therapeutics: Consultancy; Verastem: Consultancy. Samson:Curis, Inc: Employment, Equity Ownership. Atoyan:Curis, Inc: Employment, Equity Ownership. Ma:Curis, Inc: Employment, Equity Ownership. Xu:Curis, Inc: Employment, Equity Ownership. Dellarocca:Curis, Inc: Employment, Equity Ownership. Modafferi:Curis, Inc: Employment, Equity Ownership. Borek:Curis, Inc: Employment, Equity Ownership. Zhang:Curis, Inc: Employment, Equity Ownership. Parker:Curis, Inc: Employment, Equity Ownership. Whitney:Curis, Inc: Employment, Equity Ownership. Wang:Curis, Inc: Employment, Equity Ownership. Tuck:Curis, Inc: Employment, Equity Ownership. Younes:Merck: Honoraria; Roche: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Pharmacyclics: Research Funding; Celgene: Honoraria; Abbvie: Honoraria; Seattle Genetics: Honoraria; Sanofi: Honoraria; Takeda: Honoraria; Incyte: Honoraria; Bayer: Honoraria; BMS: Honoraria, Research Funding; J&J: Research Funding; Novartis: Research Funding; Genentech: Research Funding; Astra Zeneca: Research Funding; Curis: Research Funding.

Description: We have used an approach using 2-dimensional gel electrophoresis with mass spectrometry analysis combined with oligonucleotide chip hybridization for a comprehensive and quantitative study of the temporal patterns of protein and mRNA expression during myeloid development in the MPRO murine cell line. This global analysis detected 123 known proteins and 29 “new” proteins out of 220 protein spots identified by tandem mass spectroscopy, including proteins in 12 functional categories such as transcription factors and cytokines. Bioinformatic analysis of these proteins revealed clusters with functional importance to myeloid differentiation. Previous analyses have found that for a substantial number of genes the absolute amount of protein in the cell is not strongly correlated to the amount of mRNA. These conclusions were based on simultaneous measurement of mRNA and protein at just a single time point. Here, however, we are able to investigate the relationship between mRNA and protein in terms of simultaneous changes in their levels over multiple time points. This is the first time such a relationship has been studied, and we find that it gives a much stronger correlation, consistent with the hypothesis that a substantial proportion of protein change is a consequence of changed mRNA levels, rather than posttranscriptional effects. Cycloheximide inhibition also showed that most of the proteins detected by gel electrophoresis were relatively stable. Specific investigation of transcription factor mRNA representation showed considerable similarity to those of mature human neutrophils and highlighted several transcription factors and other functional nuclear proteins whose mRNA levels change prominently during MPRO differentiation but which have not been investigated previously in the context of myeloid development. Data are available online athttp://bioinfo.mbb.yale.edu/expression/myelopoiesis.

Description: Surface membrane-associated growth factors are being recognized as important for developmental processes, including cell assembly, differentiation, and growth. To investigate the role of membrane-bound macrophage colony-stimulating factor (M-CSF) in myelopoiesis, and whether this factor is released from the cell surface in association with shed membrane-derived vesicles, COS-1 cells were transfected with cDNAs for M-CSF-tau (containing the transmembrane domain) or a soluble mutant form of the molecule lacking the transmembrane domain ([s]M-CSF- alpha). COS-1 cells transfected with either cDNA released activity into the spent culture medium. Conditioned medium was separated by centrifugation into supernatants and pellets were found to contain plasma membrane-derived vesicles by transmission electron microscopy. When medium fractions were assayed in marrow cultures, activity was localized to shed plasma membrane-derived vesicles in medium conditioned by cells transfected with cDNA for M-CSF-tau and in the vesicle-free supernatants of medium conditioned by cells transfected with cDNA for [s]M-CSF-alpha. In addition, nuclear, mitochondrial, and plasma membrane subfractions of stably transfected cells were prepared and assayed for activity. Concentration-dependent stimulation of macrophage colony formation was observed with purified plasma membranes (but not nuclear or cytosolic proteins) from cells transfected with cDNA for M-CSF-tau. By contrast, membranes from untransfected cells and cells transfected with cDNA for [s]M-CSF-alpha or control DNA expressed no activity. Together, the data indicate that human M-CSF is expressed at the cell surface and exfoliated in association with surface membrane- derived vesicles.

Description: Abstract 1456 Poster Board I-479 USF1 and USF2 are ubiquitously expressed basic helix-loop-helix leucine zipper proteins that participate in a large number of biologic processes. USF1 and USF2 bind DNA as homodimers or heterodimers, typically binding E box consensus motifs. One role of USF proteins is functioning as transcription factors. Although ubiquitously expressed, they regulate expression of many cell-type and developmental-stage specific genes, such as hepcidin in hepatocytes and surfactant protein A in fetal lung cells. Another role of USF proteins is in the maintenance of chromatin architecture in barrier insulator elements, such as the well characterized 5'HS4 insulator element in the chicken beta-globin locus. In mammalian erythroid cells, USF1 and USF2 participate in the regulation of beta-globin transcription, interacting both at hypersensitive site 2 (HS2) of the beta-globin locus control region (LCR) and at the beta-globin promoter. Depletion of USF proteins leads to decreased beta-globin production. We hypothesize that in addition to beta-globin, USF proteins are important for regulation of many erythroid expressed genes. To address this hypothesis, chromatin immunoprecipitation with antibodies against USF1 and USF2 was coupled with ultra high throughput, massively parallel sequencing (Illumina Solexa sequencing, ChIP-seq) to generate a genome-wide map of USF1 and USF2 occupancy in primary erythroid cells. To generate cells for ChIP and mRNA expression profiling, human CD34+ cells isolated from peripheral blood were cultured in serum free media with erythropoietin to induce erythroid differentiation. After 14 days in culture, FACS analysis was used to confirm cells were positive for both CD 71 and glycophorin A (the R3/R4 stage of erythroid development). mRNA transcript analyses were performed using Illumina human V6-2 expression arrays and quantitative real time RT-PCR. ChIP-seq experiments for USF1 and USF2 were done in duplicate and only binding sites present in both ChIP-seq replicates were included in data analyses. A total of 20450 USF1 and 21128 USF2 sites of occupancy were identified. Co-localization of USF1 and USF2 was common, with 16739 sites binding both USF1 and USF2 (81.9% of USF1 sites and 79.2% of USF2 sites). In an analysis of a subset of erythroid expressed focus genes, USF binding was associated with active transcription. In agreement with previous studies, there was binding of USF proteins in the beta-globin LCR, and beta-globin promoter. USF binding most commonly occurred close to annotated genes, with 48.5% of USF1 sites, 44.6% of USF 2 sites and 53.0% of sites of USF1-USF2 co-localization located within 1 kb of a transcription start site (TSS), supporting the role of USF proteins as a transcription factor in these locations. A small, but significant, number of USF binding sites were located in intergenic regions 〉 100 kb from any annotated TSS. (1206 USF1, 1408 USF2, and 776 USF1-USF2). Interestingly, at sites of intergenic binding, USF1 and USF2 were much less likely to co-localize, (64% of USF1 and 55% of USF2 sites), implying that the USF proteins serve a different function at these remote binding sites than at sites of binding in close proximity to a TSS. USF proteins can bind DNA in an E-box dependent or independent manner. The Weeder Algorithm (Pavesi, Bioinformatics, 2001) was used to determine the most common binding motifs for USF1 and USF2. Over-represented motifs at sites of USF1 and USF2 binding were similar, with the most common sequences being a canonical E-box, CACGTG, as well as the related sequences ACGTGA and TCACGT. This genome-wide map of USF binding correlated with mRNA expression data indicates that USF proteins serve several different, important functions throughout the human genome and support the hypothesis that USF proteins participate in the regulation of many erythroid-expressed genes. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4585 Post-translational histone modifications influence expression by creating a chromatin environment which is conducive to or inhibitory of transcription. Modifications such as trimethylation of histone H3 lysine 4 and acetylation of histone H3 lysine 9 are generally associated with euchromatin and gene activation, while modifications such as trimethylation of histone H3 lysine 27 are associated with regions of heterochromatin and/or gene repression. Monomethyl histone H3 lysine 27 (H3K27me1) is a poorly studied post-translational histone modification for which variable associations with mRNA expression have been observed. Initially, H3K27me1 was localized to areas of pericentric heterochromain and was thought to be a marker of gene repression. Later reports described H3K27me1 enrichment throughout the body of actively transcribing genes (Vakoc C et al. MCB 26:9185, 2006; Wang Z, 40:897 Nat Genet, 2008). Some reports describe selective depletion of H3K27Me1 at promoters and transcription start sites (TSS), implying that depletion of H3K27me1 at the TSS is necessary for active transcription, (Vakoc C et al.), while others have associated increased enrichment for H3K27me1 at the promoter with increased levels of mRNA expression (Barski A et al. Cell 129:823, 2007). We hypothesize that the relationship between H3K27me1 occupancy and gene expression varies depending on both the cell-type and the location in the gene (i.e. promoter, transcription start site (TSS) and body of the gene) and that varying H3K27me1 levels in each of these locations is associated with alterations in the level of mRNA expression. To assess the association of H3K27me1 level with mRNA expression, H3K27me1 binding was determined using chromatin immunoprecipitation on microarray analysis (ChIP-chip) and correlated with mRNA levels determined using Illumina human expression arrays. ChIP-chip was performed using an antibody specific for H3K27me1 and the resulting DNA applied the to a custom designed genomic tiling NimbleGen microarray containing over 100 erythroid expressed genes and 10-100kb of flanking DNA for each locus. Probes were tiled with 10-100bp spacing, typically ∼65bp. Regions of repetitive DNA were excluded. ChIP-chip was performed in erythroid (K562) and non-erythroid (SY5Y-neural, RD-muscle) cells and the pattern of H3K27me1 enrichment assessed. mRNA transcript analyses were performed using Illumina human V6-2 expression arrays and quantitative real time RT-PCR. H3K27me1 levels at the promoter (-1000 to +1), in the 200bp surrounding the TSS (-100 to +100), and over the body of the gene were correlated with the level of mRNA expression. Increasing levels of H3K27me1 over the body of the gene lead correlated with increased levels of gene expression (R2=0.6122), while the amount of H3K27me1 at the promoter (-1000 to +1) had no correlation with gene expression (R2=0.2769). In agreement with Vakoc et al., decreased enrichment for H3K27Me1 at the TSS (-100 to +100) correlated with increased levels of mRNA expression. This is in sharp contrast to H3K4Me3, which accumulates at the start site of active genes. H3K27me1 has not been studied in detail in transcriptionally silent genes. Interestingly, genes without H3K27Me1 enrichment had no expression, implying that H3K27me1 is a marker of active transcription. Patterns of H3K27Me1 enrichment were cell-type specific. For example, in erythroid (K562) cells, the beta-globin locus was highly enriched for H3K27me1. This enrichment was not present in non-erythroid cells (RD, SY5Y). Finally, H3K27Me1 may also mark enhancers in a cell type-specific manner. For example, in the well studied HS2 enhancer in the beta-globin LCR, there is significant enrichment for H3K27me1 in K562 cells, but not in SY5Y or RD cells. These data indicate that modulation of chromatin architecture by monomethylation of histone 3 lysine 27 influences the level of gene expression in erythroid and non-erythroid cells. Disclosures: No relevant conflicts of interest to declare.

Description: With the goal of creating a resource for in-depth study of myelopoiesis, we have executed a 2-pronged strategy to obtain a complementary DNA (cDNA) clone set enriched in hematopoietic genes. One aspect is a library subtraction to enrich for underrepresented transcripts present at early stages of hematopoiesis. For this, a hematopoietic cDNA library from primary murine bone marrow cells enriched for primitive progenitors was used as tester. The subtraction used 10 000 known genes and expressed sequence tags (ESTs) as driver. The 2304 randomly picked clones from the subtracted cDNA libraries represent 1255 distinct genes, of which 622 (50%) are named genes, 386 (30%) match uncharacterized ESTs, and 247 (20%) are novel. The second aspect of our strategy was to complement this subtracted library with genes known to be involved in myeloid cell differentiation and function. The resulting cDNAs were arrayed on polylysine-coated glass slides. The microarrays were used to analyze gene expression in primary and cultured murine bone marrow–derived progenitors. We found expression of various types of genes, including regulatory cytokines and their receptors, signal transduction genes, and transcription factors. To assess gene expression during myeloid differentiation, we examined patterns of change during induced differentiation of EML cells. Several hundred of the genes underwent fluctuations in expression level during myeloid cell differentiation. The complete database, accessible on the World Wide Web at http://yale130132115135.med.yale.edu/, allows for retrieval of information regarding these genes. Our microarray allows for genomewide expression analysis of myeloid stem cells, which will help in defining the regulatory mechanisms of stem cell differentiation.

Description: CD20-targeted radioimmunotherapy is a promising new treatment for B-cell non-Hodgkin lymphoma (NHL). We now provide updated and long-term data on 59 chemotherapy-relapsed/refractory patients treated with iodine 131I tositumomab in a phase I/II single-center study. Fifty-three patients received individualized therapeutic doses, delivering a specified total-body radiation dose (TBD) based on the clearance rate of a preceding dosimetric dose. Six patients received dosimetric doses only. Dose-escalations of TBD were conducted separately in patients who had or had not undergone a prior autologous stem cell transplant (ASCT) until a nonmyeloablative maximally tolerated TBD was established (non-ASCT = 75 cGy, post-ASCT = 45 cGy). Fourteen additional non-ASCT patients were treated with 75 cGy. Unlabeled antibody was given prior to labeled dosimetric and therapeutic doses to improve biodistribution. Forty-two (71%) of 59 patients responded; 20 (34%) had complete responses (CR). Thirty-five (83%) of 42 with low-grade or transformed NHL responded versus 7 (41%) of 17 with de novo intermediate-grade NHL (P = .005). For all 42 responders, the median progression-free survival was 12 months, 20.3 for those with CR. Seven patients remain in CR 3 to 5.7 years. Sixteen patients were re-treated after progression; 9 responded and 5 had a CR. Reversible hematologic toxicity was dose limiting. Only 10 patients (17%) had human anti-mouse antibodies detected. Long-term, 5 patients developed elevated thyroid-stimulating hormone levels, 5 were diagnosed with myelodysplasia and 3 with solid tumors. A single, well-tolerated treatment with iodine 131I tositumomab can, therefore, produce frequent and durable responses in NHL, especially low-grade or transformed NHL.

Description: CD20-targeted radioimmunotherapy is a promising new treatment for B-cell non-Hodgkin lymphoma (NHL). We now provide updated and long-term data on 59 chemotherapy-relapsed/refractory patients treated with iodine 131I tositumomab in a phase I/II single-center study. Fifty-three patients received individualized therapeutic doses, delivering a specified total-body radiation dose (TBD) based on the clearance rate of a preceding dosimetric dose. Six patients received dosimetric doses only. Dose-escalations of TBD were conducted separately in patients who had or had not undergone a prior autologous stem cell transplant (ASCT) until a nonmyeloablative maximally tolerated TBD was established (non-ASCT = 75 cGy, post-ASCT = 45 cGy). Fourteen additional non-ASCT patients were treated with 75 cGy. Unlabeled antibody was given prior to labeled dosimetric and therapeutic doses to improve biodistribution. Forty-two (71%) of 59 patients responded; 20 (34%) had complete responses (CR). Thirty-five (83%) of 42 with low-grade or transformed NHL responded versus 7 (41%) of 17 with de novo intermediate-grade NHL (P = .005). For all 42 responders, the median progression-free survival was 12 months, 20.3 for those with CR. Seven patients remain in CR 3 to 5.7 years. Sixteen patients were re-treated after progression; 9 responded and 5 had a CR. Reversible hematologic toxicity was dose limiting. Only 10 patients (17%) had human anti-mouse antibodies detected. Long-term, 5 patients developed elevated thyroid-stimulating hormone levels, 5 were diagnosed with myelodysplasia and 3 with solid tumors. A single, well-tolerated treatment with iodine 131I tositumomab can, therefore, produce frequent and durable responses in NHL, especially low-grade or transformed NHL.